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Unread 06-19-2003, 09:42 AM   #170
bigben2k
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Join Date: May 2002
Location: Texas, U.S.A.
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Quote:
Originally posted by Since87
a. Which MOSFET is the "2nd mosfet"? When you say, the reason is "the internal body diode", are you referring to the internal body diode of the second MOSFET or the first?

b. If one MOSFET's gate is saturated, then both will be saturated. There is nothing preventing reverse current flow when both MOSFET's are 'on'.
Right, but if the driver is operating from the PWR_Good line, it should shut off, when the PSU is OFF, and with the additional diode, it should prevent the MOSFETs from seeing any voltage. With both MOSFETs, there shouldn't be any leaks back into the PSU that's off, because the internal diode of the backward MOSFET.

The problem I see is the potentially unpredictable behavior of the MOSFET, when used backwards. And I still need a better driver for the +12 line.


But back to what you're saying: when the gates are saturaded, what prevents current from leaking back?

Given a 4 milliohm resistance, I have to assume that the voltage drop across a single MOSFET would be around 0.16 volts (@ 40 amps) and 4 millivolts (@ 1 amp).

The MOSFETs "thermally stabilize", as that's the balancing principle here, combined with the trim pots to fine tune the voltage differences (That's the way I understand it :shrug: ).

I don't know!
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